Cold Storage for Film: A New Use for Your Refrigerator's Vegetable Bin
Film is perishable and storing it in the refrigerator can help keep it fresh until you get a chance to use it. It needs time to warm up before you load it in your camera though. If you open the canister before it has time to reach room temperature, moisture from the air will condense on the film surface causing spots on your pictures. To prevent this, be sure to take it out at least an hour before opening the canister.
I'm not a big fan of storing film in the freezer, but you can do it. Hidden behind your frozen dinners and ice cube trays, film will actually keep for a good year beyond its expiration date, but this hardly seems necessary. Personally, I'd rather just buy fresh film closer to when I'm going to use it; the refrigerator gives me plenty of flexibility without resorting to freezing film. If you do feel compelled to store it in the freezer, just remember to allow at least an extra hour for your film to warm up before using it since it's starting out even colder than the 'fridge.
Update: I recently came across this page on Kodak's site recommending one hour when coming from the fridge and an hour and a half from the freezer. There you have it, the official word straight from the source.